Recently, along with increasing demands for mobile communications, IMT-2000 (International Mobile Telecommunication) regarded as a third generation mobile communication system, in particular, is realizing unprecedented high-speed and wide transmission. It is expected that a mobile environment using features of this communication system will be particularly valued for multimedia communications such as moving image communications.
Development of a distributed radio network system having flexibility and extendability is currently considered. For example, Nonpatent Literature 1 has been laid down as a technical report in Mobile Wireless Internet Forum.
FIG. 15 is a block diagram of a functional model of a radio network system disclosed in the Nonpatent Literature 1. In this radio network system, a radio base station 30 is referred to as “Node B” in a third generation mobile communication system. Notification of system information, survey of radio environments, coding and decoding of a radio channel, detection of random access, measurement of unlink outer loop power, downlink outer loop power control, and uplink inner loop power control are performed on a radio layer 1 denoted by reference numeral 31 in FIG. 15.
An RNC (Radio Network Controller) 32 is divided to a Control/Drift RNC 33 and a Serving RNC 34. The Control/Drift RNC 33 includes functions configured by a cell bearer gateway 35, a cell controller 36, a common radio resource management 37, a paging/broadcast 38, and a UE GEO location 39. The Serving RNC 34 includes functions configured by a UE GEO location 39, a user radio gateway 40, and a mobile control 41.
The cell bearer gateway 35 performs common channel multiplexing and demultiplexing and data transmission on a broadcast and multicast radio bearer. The cell controller 36 performs control over assignment and congestion with respect to radio resources, assignment of discrete physical radio resources, assignment of common logic radio resources, management of assignment and configuration of dynamic common physical resources, control over notification of system information, measurement and collection of cell environments, assignment of a dynamic channel, cell paging, and downlink open loop power control. The common radio resource management 37 measures and collects radio network environments and optimizes a network load. The paging and broadcast 38 performs control over a broadcast flow or a multicast flow of the radio bearer, notification of a broadcast or multicast state of the radio bearer, adjustment of a call to a mobile terminal in multi cells, and adjustment of a call to the mobile terminal. The UE GEO location 39 collects and calculates information on a position of the mobile terminal.
The user radio gateway 40 performs segmentation and assembling, confirmation of discrete channel transmission, header compression, discrete channel multiplexing and demultiplexing, macro diversity combining and splitting, processing for the uplink outer loop power control, measurement of radio media access, and radio channel encryption. The mobile control 41 performs assignment of discrete logic radio resources, management of configurations of discrete physical radio resources, control over flows of discrete radio packets, adjustment of assignment control, management of contexts of the radio resources, trace, connection setting and unsetting, mobile terminal measurement control, uplink outer loop power control, adjustment of the downlink outer loop power control, mapping of the radio discrete packet flow to a radio QoS, mapping of the radio bearer to a transport QoS, location management, control over macro diversity combining and splitting, radio channel coding control, media access measurement control, TDD timing control, measurement and calculation of radio frame transmission, discrete calling to the mobile terminals, and handover control.
The functional models of the radio network system have the features in that a transport layer is completely separated from a radio network layer so as to ensure flexibility and extendability. In addition, as indicated by a one-dot chain line in FIG. 15, the radio network layer is separated into a signaling plane that serves as a control plane including the cell controller 36, the common radio resource management 37, the paging and broadcast 38, the UE GEO location 39, and the mobile control 41, and a bearer plane that serves as a user plane including the cell bearer gateway 35 and the user radio gateway 40.
Nonpatent Literature 1: Technical Report in Mobile Wireless Internet Forum, MTR-007 Open RAN Architecture in 3rd Generation Mobile Systems Release v1.0.0 (12 Jun. 2001)
According to the conventional system disclosed in the Nonpatent Literature 1, in order to provide the system with the flexibility and extendability, the respective functional blocks are defined while the radio network layer is separated into the signaling plane serving as the control plane and the bearer plane serving as the user plane. However, the Nonpatent Literature 1 does not disclose the way of synchronizing a plurality of devices (nodes) when one functional block is realized by the devices (nodes).
The present invention has been achieved in view of these circumstances. It is an object of the present invention to provide a node synchronization method for a radio network system that can reduce traffic of control messages related to node synchronization between one of a plurality of radio bearer servers that control a data transfer between a mobile terminal and a user plane (bearer plane) and one of a plurality of radio control servers that control reception of a call, and that can efficiently establish the node synchronization between the radio bearer server and the radio control server, and to provide a radio control server and a radio bearer server.